A novel PRNP-P105S mutation associated with atypical prion disease and a rare PrPSc conformation.

OBJECTIVE: To define the clinicopathologic, genetic, and pathogenic prion protein (PrP(Sc)) characteristics associated with a novel mutation of the prion protein gene (PRNP). METHODS: The coding segment of PRNP from the proband and family members was sequenced and the brain of the proband was histologically studied. The Western blot profile of the proteinase K (PK) resistant fraction of PrP(Sc), an approximation of its conformation, or "PrP(Sc)-type," was determined. RESULTS: We detected a novel mutation at codon 105 of PRNP that results in a serine (S) substitution of proline (P) (P105S), in a young woman who developed progressive aphasia, behavioral changes, dementia, and parkinsonism, lasting 10 years to her death. Histopathologic findings included an intense focus of multicentric PrP-plaques within the hippocampus, punctate plaques scattered throughout the cerebellum, and intense spongiform degeneration focally within the putamen, suggesting a variant of Gerstmann-Sträussler-Scheinker syndrome (GSS). However, PrP(Sc)-typing revealed two PK-resistant PrP(Sc) fragments (approximately 21 and 26 kDa), a pattern not previously detected in GSS. CONCLUSIONS: This mutation is the third sequence variation at codon 105 of PRNP. The unusual phenotype and PrP(Sc)-type distinguishes this genetic prion disease from typical Gerstmann-Sträussler-Scheinker syndrome and other codon 105 substitutions, suggesting that, in addition to the loss of proline at this position, the PrP(Sc) conformation and phenotype is dependent on the specific amino acid substitution.

Inherited prion disease caused by the V210I mutation: transmission to transgenic mice.

OBJECTIVE: To describe the clinical and neuropathologic profile and determine the strain characteristics of familial Creutzfeldt-Jakob disease (fCJD) caused by a point mutation of the PRNP gene at codon 210 that results in a valine-to-isoleucine substitution in the prion protein (PrP). METHODS: The clinicopathologic features of four individuals from the United States who died of fCJD(V210I) were compared. Transgenic (Tg) mice expressing a chimeric human-mouse PrP transgene were inoculated with brain extracts from three fCJD(V210I) cases, sporadic CJD (sCJD), fCJD(E200K), and fatal familial insomnia (FFI), to compare prion strain characteristics. RESULTS: The clinicopathologic profile of fCJD(V210I) was variable among cases but shared similarities with sCJD. The pattern of PrP(Sc) deposition in the brains of Tg mice was similar to that caused by sCJD but different from that associated with fCJD(E200K) or FFI. CONCLUSIONS: Each of these prion diseases is characterized by a rapidly progressive dementia with myoclonus, periodic complexes on EEG, and spongiform change without PrP plaque deposition in the brain. The occurrence of a different PrP(Sc) phenotype with each PRNP mutation argues that each respective amino acid sequence substitution produces a different prion strain.

The prion diseases.

The prion diseases constitute an unusual group of neurodegenerative disorders. Although they are similar in many ways to other more common diseases, such as Alzheimer disease and amyotrophic lateral sclerosis, they are set apart on the basis of their transmissible nature. In addition to the unique feature of transmissibility, the prion diseases demonstrate that the expression of diverse disease phenotypes is possible from a common etiologic factor. This review provides the reader with a basic understanding of the nature of prions and highlights the clinical and pathologic features of these fascinating diseases.

Amyotrophy in prion diseases.

Amyotrophic lateral sclerosis was once thought to be caused by persistent viral infection, partly because some patients with transmissible Creutzfeldt-Jakob disease showed prominent amyotrophy. However, in the past 15 years there has been little interest in the amyotrophy in prion diseases, and the possible link to amyotrophic lateral sclerosis has been eschewed. We analyzed case reports of prion disease published after 1968 for evidence of amyotrophy. We defined amyotrophy as clinically evident fasciculation buttressed by electromyographic results in some cases. We sought evidence of motor neuron degeneration at autopsy. Prion disease was proved by transmissibility, immunohistochemistry demonstration of protease-resistant prion protein, or finding a mutation in the prion protein gene. Amyotrophy was noted in 27 patients: 13 with sporadic Creutzfeldt-Jakob disease, 2 with familial Creutzfeldt-Jakob disease, and 12 with Gerstmann-Sträussler-Scheinker disease. Of the 27, 23 showed clinical fasciculation and 10 had electromyographic evidence of denervation. The spinal cord was examined in 8 patients: 6 showed loss of motor neurons, 1 showed vacuolation of motor neurons, and 1 reported no abnormalities. Another 23 patients had typical histopathological characteristics but lacked molecular or biochemical proof of prion disease. The total number of patients with amyotrophy and proven prion disease that we identified was 50. This case review supports the belief that amyotrophy is occasionally a prominent feature of Creutzfeldt-Jakob disease and underscores the importance of documenting lower motor neuron function and the crucial role of examining the spinal cord at autopsy in cases of prion disease.

A familial case of Alzheimer's disease without tau pathology may be linked with chromosome 3 markers.

Alzheimer's disease is the most common form of dementia that occurs in later years. The diagnosis is confirmed by the pathological findings of betaA4-amyloid-containing neuritic plaques and neurofibrillary tangles, the former being present in sufficient quantity commensurate with age. Other forms of dementia are more difficult to diagnose clinically; their pathology is noted for the lack of plaques and tangles. A patient with a family history of dementia presented with the clinical signs of Alzheimer's disease which lasted for 13 years. At autopsy the brain tissue had betaA4-amyloid-containing neuritic plaques, but no neurofibrillary tangles (i.e., the tissue was negative for staining with the tau antibody). Genetic analysis of DNA from family members revealed no linkage with chromosome 17 markers, indicating that this was not frontotemporal dementia. However, there was linkage with chromosome 3 markers. Thus, this form of Alzheimer's disease with a pathology of plaques only is linked with markers on chromosome 3.

Creutzfeldt-Jakob disease (CJD) after blood product transfusion from a donor with CJD.

We report a second case of an association between an albumin transfusion and Creutzfeldt-Jakob disease. On balance, we believe our case represents a chance and not a causal relation.

A transmembrane form of the prion protein in neurodegenerative disease.

At the endoplasmic reticulum membrane, the prion protein (PrP) can be synthesized in several topological forms. The role of these different forms was explored with transgenic mice expressing PrP mutations that alter the relative ratios of the topological forms. Expression of a particular transmembrane form (termed CtmPrP) produced neurodegenerative changes in mice similar to those of some genetic prion diseases. Brains from these mice contained CtmPrP but not PrPSc, the PrP isoform responsible for transmission of prion diseases. Furthermore, in one heritable prion disease of humans, brain tissue contained CtmPrP but not PrPSc. Thus, aberrant regulation of protein biogenesis and topology at the endoplasmic reticulum can result in neurodegeneration.

The prion diseases: Creutzfeldt-Jakob, Gerstmann-Sträussler-Scheinker, and related disorders.

The prion diseases are an interesting group of neurodegenerative disorders for a variety of reasons. The most obvious is their property of transmissibility, but beyond that they constitute a fascinating example of the diversity of disease expression possible from a common etiologic factor. Thought of as "strains" in animals and phenotypes in humans, these varied expressions of prion disease are most likely due to subtle conformational changes in the pathogenic form of the prion protein. These strain-like characteristics are best exemplified in the genetic varieties of human prion disease in which specific mutations are associated with specific phenotypic profiles. This review attempts to highlight the clinical and pathologic features of the prion diseases with a particular focus on the genetic determinants that define the various familial forms and that modify sporadic and iatrogenic forms of the disease.

Changes of hippocampal N-acetyl aspartate and volume in Alzheimer's disease. A proton MR spectroscopic imaging and MRI study.

Hippocampal atrophy detected by MRI is a prominent feature of early Alzheimer's disease (AD), but it is likely that MRI underestimates the degree of hippocampal neuron loss, because reactive gliosis attenuates atrophy. We tested the hypothesis that hippocampal N-acetyl aspartate (NAA: a neuronal marker) and volume used together provide greater discrimination between AD and normal elderly than does either measure alone. We used proton MR spectroscopic imaging (1H MRSI) and tissue segmented and volumetric MR images to measure atrophy-corrected hippocampal NAA and volumes in 12 AD patients (mild to moderate severity) and 17 control subjects of comparable age. In AD, atrophy-corrected NAA from the hippocampal region was reduced by 15.5% on the right and 16.2% on the left (both p < 0.003), and hippocampal volumes were smaller by 20.1% (p < 0.003) on the right and 21.8% (p < 0.001) on the left when compared with control subjects. The NAA reductions and volume losses made independent contributions to the discrimination of AD patients from control subjects. When used separately, neither hippocampal NAA nor volume achieved to classify correctly AD patients better than 80%. When used together, however, the two measures correctly classified 90% of AD patients and 94% of control subjects. In conclusion, hippocampal NAA measured by 1H MRSI combined with quantitative measurements of hippocampal atrophy by MRI may improve diagnosis of AD.

Mutation of the prion protein gene at codon 208 in familial Creutzfeldt-Jakob disease.

Four point mutations and one insertion within the prion protein (PrP) gene have been tightly linked to the development of inherited prion disease. We developed a denaturing gradient gel electrophoresis system that allowed us to screen the entire open reading frame of the PrP gene. Using this system, we found a new mutation of the PrP gene in a patient with pathologically confirmed Creutzfeldt-Jakob disease and a negative family history for dementia. DNA sequencing revealed an adenine substitution for guanine at the second position of codon 208, which results in the nonconservative substitution of histidine for arginine. The same PrP mutation was identified in another younger member of the pedigree but was not present in more than 200 alleles tested. Such findings suggest that the frequency of inherited prion disease might be higher than ascertained by clinical history alone.

Prion disease (PrP-A117V) presenting with ataxia instead of dementia.

Gerstmann-Sträussler-Scheinker disease (GSS) is caused by several different point mutations of the prion protein (PrP) gene, each of which generally produces a distinct clinical phenotype. An ataxic form of GSS is genetically linked to a mutation at codon 102 (CCG-->CTG) leading to the substitution of leucine for proline, while a "telencephalic" variant of GSS, in which dementia is the predominant symptom and ataxia is minimal, has been described in two kindreds with a mutation at codon 117 (GCA-->GTG) resulting in the substitution of valine for alanine. In this report, we present a family with ataxic GSS that has, however, the same mutation at codon 117 as is present in the telencephalic variant of GSS. Other than an additional silent mutation (GCA-->GCG) at codon 117 on the normal allele, there were no other mutations detected. At the polymorphic codon 129, valine was encoded by both alleles in the proband that we studied. Why this family with prion disease (PrP-A117V) should present with ataxia instead of dementia, which was found in two previously identified families with the same PrP gene mutation, remains to be established.

Complete penetrance of Creutzfeldt-Jakob disease in Libyan Jews carrying the E200K mutation in the prion protein gene.

BACKGROUND: Creutzfeldt-Jakob disease (CJD) is a prion disease which is manifest as a sporadic, inherited, and transmissible neurodegenerative disorder. The mean age at onset of CJD is approximately 60 years, and as such, many people destined to succumb undoubtedly die of other illnesses first. The delayed onset of CJD has complicated the analysis of inherited forms of the illness and led to the suggestion that mutations in the prion protein (PrP) gene are necessary but not sufficient for prion disease despite genetic linkage; indeed, an environmental factor such as a ubiquitous virus has been proposed as a second necessary factor. MATERIALS AND METHODS: To examine what appeared to be incomplete penetrance, we applied a life-table analysis to clinical and pedigree data from a cluster population of Libyan Jews in which the E200K mutation is prevalent. The study population included 42 affected and 44 unaffected members of 13 Libyan Jewish families, all of whom possessed the E200K mutation. RESULTS: The calculated value using life table analysis is 0.77 at age 70 which increases to 0.89 if a mutation carrier survives to age 80 and 0.96 if age 80 is surpassed. CONCLUSIONS: These data argue that the E200K mutation alone is sufficient to cause prion disease and does so in an age-dependent manner.

Isolated fascicular abducens nerve palsy and Lyme disease.

A patient with Lyme disease developed an isolated sixth nerve palsy at the end of a 1 month course of oral antibiotics. Magnetic resonance imaging disclosed high-signal abnormality at the left pontomedullary junction, implicating involvement of the distal sixth nerve fascicle. Although facial numbness ensued during a subsequent course of intravenous antibiotics, corticosteroid therapy was associated with prompt improvement of neurologic signs, suggesting an immunologic mechanism for the central nervous system dysfunction.

Activation of central mu-opioid receptors is involved in clonidine analgesia in rats.

The analgesic effect of clonidine in spontaneously hypertensive rats (SHR) and in normotensive Sprague-Dawley (SD) rats was assessed by using the formalin pain test. The analgesic response of SD rats to low doses (15-60 micrograms/kg i.p.) but not to a high dose (150 micrograms/kg i.p.) of clonidine was inhibited by naloxone, 2 mg/kg i.p., and similar interaction was noted in SHR. In both rat strains, the analgesic response to low i.p. doses of clonidine was also inhibited by injection of 5 micrograms of naloxone or 7 micrograms of beta-funaltrexamine, a mu-receptor antagonist, into the lateral cerebral ventricle. I.c.v. injection of 5 micrograms of ICI 174864, a delta-receptor antagonist, potentiated or did not influence clonidine analgesia in SD rats and SHR, respectively. It is concluded that the analgesic response to clonidine involves activation of central mu-opioid receptors in both SHR and SD rats, possibly by an endogenous opioid released by clonidine.

Activation of brainstem endorphinergic neurons causes cardiovascular depression and facilitates baroreflex bradycardia.

The effects of electrical stimulation of the arcuate nucleus on blood pressure, heart rate and baroreflex sensitivity were studied in urethane-anesthetized Sprague-Dawley rats. Stimulation of the mid-anterior parts of the arcuate nucleus at 80 Hz, 0.8 ms and 50-200 microA caused a biphasic, depressor/pressor, response and moderate bradycardia. Intravenous administration of a vasopressin V1-receptor antagonist eliminated the pressor component and unmasked a pure depressor response. This depressor response could be inhibited by naltrexone, 2 mg/kg i.v., by an antiserum against beta-endorphin, 100 nl injected directly into the ipsilateral nucleus tractus solitarii, or by deafferentation of the dorsal vagal complex (nucleus tractus solitarii and dorsal vagal nucleus) by an ipsilateral, dorsolateral knife-cut of the medulla oblongata. Stimulation of the arcuate nucleus at currents of 20-40 microA did not influence basal blood pressure or heart rate but potentiated the reflex bradycardia induced by phenylephrine, and this effect was completely blocked by naltrexone. It is concluded that a beta-endorphin-containing pathway projecting from the arcuate nucleus to the ipsilateral dorsal vagal complex is involved in depressor cardiovascular regulation and in the facilitation of baroreflex bradycardia.

Endorphinergic mechanism in the central cardiovascular and analgesic effects of clonidine.

In urethane-anesthetized male rats, injection of 5 nmol clonidine into the nucleus of the solitary tract (NTS) causes hypotension and bradycardia. These effects are greater in spontaneously hypertensive rats (SHR) and normotensive Sprague-Dawley (SD) rats than in normotensive Wistar-Kyoto (WKY) rats. The effects of clonidine are stereoselectively inhibited by 100 ng intra-NTS naloxone in SHR and SD but not in WKY rats. In SHR, the effects of clonidine are also inhibited by intra-NTS administration of ICI 174864 (a delta-receptor antagonist) but not by beta-funaltrexamine (a mu-receptor antagonist), while in SD rats only the mu- and not the delta-antagonist was effective. Neonatal treatment of SHR with monosodium glutamate (MSG) reduced the beta-endorphin content of the arcuate nucleus and the NTS, reduced the cardiovascular effects of clonidine, and abolished their naloxone sensitivity. MSG treatment of newborn WKY reduced the beta-endorphin content of the arcuate nucleus but not the NTS and did not affect the responses to clonidine. Measurement of pain sensitivity by the formalin test indicated that clonidine was more potent as an analgesic in SHR and SD than in WKY rats, and its effect was inhibited by naloxone (2 mg/kg i.p.) in the former two strains but not in WKY. It is proposed that a naloxone-sensitive component of the cardiovascular effects of clonidine is due to release of a beta-endorphin-like opioid from the NTS, and that this mechanism is present in SHR and SD but not in WKY rats.(ABSTRACT TRUNCATED AT 250 WORDS)

On the relationship between clonidine hypotension and brain beta-endorphin in the spontaneously hypertensive rat: studies with alpha adrenergic and opiate blockers.

The relationship between the centrally mediated hypotensive and bradycardic effects of clonidine to central alpha-2 adrenergic receptor activation, brain beta-endorphin (BE) release and opiate receptor activation was studied in chloralose-anesthetized spontaneously hypertensive rats (SHRs) and Wistar-Kyoto rats, using a cerebroventricular perfusion system. Prior treatment of SHRs with i.v. naloxone (2 or 4 mg/kg) or i.c.v. yohimbine (10 or 20 micrograms/kg) reduced the hypotension and bradycardia induced by i.c.v. clonidine, but in Wistar-Kyoto rats naloxone had no similar blocking effects. Prazosin (20 micrograms/kg i.c.v.) reduced the clonidine bradycardia but not the hypotension in SHRs. Hypotension in the SHRs due to i.c.v. alpha-methylnorepinephrine (20 micrograms/kg) was reduced by both naloxone and yohimbine whereas alpha-methylnorepinephrine bradycardia was reduced by yohimbine but not by naloxone. Prior hypothalamic lesions in the SHRs reduced clonidine hypotension, but not bradycardia, and interfered with naloxone blockade of the residual clonidine hypotensive effect. Clonidine lowered immunoreactive BE levels in SHR hypothalamus, medulla and pituitary but did not change BE levels in the i.c.v. perfusate. The findings support the idea that in the SHRs, clonidine hypotension results from alpha-2 adrenergic stimulation of brain, causing BE release and central opiate receptor activation, and they suggest that the hypothalamus is involved in these interactions. Also, clonidine hypotension and bradycardia appear to involve different mechanisms in brain.

An intracerebroventricular perfusion system developed for the study of centrally acting antihypertensive drugs in the rat.

A method for the complete construction and employment of an intracerebroventricular perfusion system for the rat brain is described. Rats maintained on the system for up to 7 hr displayed no detectable change in cardiovascular status. Penetration of intracerebroventricular-administered methylene blue dye into all areas of the cerebroventricles demonstrated the accessibility of the injection volume throughout the ventricular system. The hypotensive and bradycardic response produced by a 1.5-microgram/kg dose of clonidine (a centrally active antihypertensive agent) administered via the intracerebroventricular implant was of considerably greater magnitude and duration than an equivalent intravenous dose. Administration of [3H]-labeled clonidine via the intracerebroventricular implant resulted in relatively minor accumulation of the drug into peripheral organs, when compared to that found in the brain. These supportive data suggest the general applicability of this approach for studying the selective central effects of pharmacologic agents in a relatively inexpensive and easily procured laboratory animal.

Acute tolerance to clonidine hypotension and bradycardia in normotensive and hypertensive rats.

Tolerance to the antihypertensive effect of clonidine has been observed in humans but there are few studies showing either acute or chronic tolerance to clonidine hypotension in experimental animals. We determined whether tachyphylaxis to acute clonidine hypotension could be demonstrated in normotensive Sprague Dawley rats by i.v. injections of 2 repetitive clonidine doses of either 1.5, 3.0, 5.0, or 10.0 micrograms/kg, or in SHR rats by repeated intracerebroventricular injections of 1.5 or 3.0 micrograms/kg, while monitoring arterial blood pressure. Second doses of clonidine were given 30 minutes after recovery of arterial pressure from the first dose. At 3.0 micrograms/kg and greater, the hypotension produced by the second dose was at least 50% less than that elicited by the first dose. By contrast, no acute tachyphylaxis was observed to the decrease in tension caused by clonidine in the transmurally stimulated isolated guinea pig ileum after 2 repeated exposures to clonidine, with intervening wash, at concentrations between 5 X 10(-10) M to 5 X 10(-8) M. Also, no tachyphylaxis occurred to the initial hypertensive phase of clonidine in Sprague Dawley rats.